The present invention relates to a stator structure of electromagnetic motors, generators, etc. and rotating electrical machines using the stator structure, and more particularly, to improvements in a fixing structure of a stator provided with coils.
Generally, a rotating electrical machine such as a DC motor and generator is comprised of a rotor provided with a rotary shaft and a stator, and in inner rotor type rotating electrical machines, such a structure is widely known that a magneto rotor is rotatably supported axially by a housing and that stator coils are arranged in the shape of a ring around the periphery of the rotor.
As shown in FIG. 10A, a rotating electrical machine is generally known which has an appearance such that a stator core C is nipped in a sandwich form between a pair of end brackets E1, E2 made of die-cast aluminum and that a rotary shaft R1 protrudes through the center. For example, the stator core C has a shape as shown in FIG. 10B as disclosed in Patent Document 1 (Japanese Unexamined Utility Model Publication No. H06-60284).
This stator core C is fabricated by layering the necessary number of magnetic plates each obtained by forming a portion to accommodate a rotor R to be rotatable in the center portion, magnetic pole portion C1, and a portion where stator coils are wound and arranged in a thin plate material C2 made of a magnetic material by press working with die-cutting. In addition, the rotor R is comprised of a magnetic rotor R2 and rotary shaft R1.
Further, in recent years, for example, Patent Document 2 (Japanese Unexamined Patent Publication No. 2004-266982) discloses an inner rotor type rotating electrical machine where the rotary shaft of the rotor is axially supported by a pair of front and rear cup-shaped brackets, magnets are disposed in the rotor to form NS magnetic poles in the rotation circumference direction, and stator coils are arranged in the shape of a circular ring around the periphery of the rotor. In the Document, a stator coil is wound around each of a plurality of divided cores via an insulator, the plurality of stator coils is held by a pair of cup-shaped brackets from the front and back of the rotary shaft, and circular magnetic teeth are formed. Then, each of a plurality of divided cores annularly arranged is fabricated by press-forming an electromagnetic steel plate, for example, a silicon steel plate into a desired shape, and layering the core pieces in a laminate form, and each stator core is thus prepared. The stator core is covered with an insulator and wound with the core, adjacent cores are fitted in a concavo-convex manner, and annular stator coils are formed.
Thus formed ring-shaped stator coils are fixed by a pair of cup-shaped brackets axially supporting the magnet rotor, and a structure of the rotating electrical machine is formed. By axially supporting the rotor rotary shaft by a pair of brackets, the magnet rotor is positioned, a plurality of stator cores is nipped by the pair of brackets, and ring-shaped stator coils are thereby arranged around the periphery of the rotor.
As described above, each of a plurality of magnetic pole portions protrudes toward the center in the stator core comprised of a single magnetic plate obtained by performing press working with die-cutting on a thin plate material made of a magnetic material as described previously. Accordingly, it is very difficult to wind the stator coil that is wound around the plurality of magnetic pole portions, and the automatic winding machine for automatically winding the coil is complicated and considerably expensive.
Therefore, in order to enable ordinary automatic winding machines to wind the stator coil with ease, each magnetic pole portion of the stator core is formed of a division core that is divided from one another, the stator coil is wound around each division core, and then, division cores are combined to form a single stator core.
However, when a stator core is formed of a plurality of division cores, the magnetic reluctance is high in the junction between division cores, a magnetic circuit is hard to form, and magnetic instability thereby occurs and becomes a factor of fluctuations in rotation.
Further, in arranging the stator coils around the magnet rotor in the shape of a ring as described previously, for the stator coils, it is general to prepare a plurality of stator cores corresponding to the magnetic teeth to arrange in the shape of a ring. For example, the number of stator cores is defined such that magnetic teeth corresponding to a multiple of 4 are formed in three-phase motors, each stator core is formed such that electromagnetic steel plates such as silicon steel plates are layered in a laminate form, the coil is wound around the periphery via an insulator, and end portions of the stator cores are coupled, for example, in a concavo-convex fit.
In the case of such a structure where a plurality of stator cores is coupled annularly to prepare the stator coils, and is sandwiched by a pair of brackets from the front and back of the rotary shaft, the thickness shape of each core becomes a problem. Referring to FIG. 7, since each stator core is configured by laminating a plurality of electromagnetic steel plates, it is extremely difficult to manufacture the stator core in a uniform thickness shape. In other words, as shown in FIG. 9, assuming that the laminate thickness of a first stator core 91a is t1 and that the laminate thickness of a second stator core 91b is t2, when the laminate thickness t1 and laminate thickness t2 are different from each other, a gap occurs in the struck surface 95a of the first bracket and the struck surface 96a of the second bracket. When the magnet rotor (not shown) rotates, each stator core rattles back and forth in the shaft direction due to the gap g, and noise and vibrations arise. Concurrently therewith, the magnetic forces of the magnetic teeth formed around the periphery of the rotor change, thereby resulting in a cause of fluctuations in rotation.
Therefore, conventionally, when such a plurality of stator cores is prepared, the thickness of the material plate of the electromagnetic steel plate, press-die structure, etc. are devised to uniform the thickness shape of each core, and the uniform thickness is thus secured. For example, when the rolled steel plate undergoes press die-cutting, die-cutting is performed along the rolling direction where fluctuations in material thickness are small, and its manufacturing is thus difficult and becomes a factor of high cost.
The present invention was made in view of the above-mentioned problems, and it is a first object of the invention to provide a stator structure and rotating electrical machine without generating noise and vibrations in action for enabling each core to be reliably fixed in arranging a plurality of cores annularly around the rotor to configure a stator even when the dimensional error occurs in manufacturing accuracy of each core.
Further, it is a second object of the invention to provide a stator structure and rotating electrical machine for enabling a plurality of cores to be fixed in a precise annular shape in alignment with one another in the shaft direction of the rotary shaft.
Furthermore, with attention directed toward a pair of end brackets nipping a stator core in a sandwich form in a rotating electrical machine such that a plurality of division cores is assembled and formed as a single stator core, it is a third object of the invention to provide a rotating electrical machine provided with stable rotation characteristics without fluctuations in rotation, by connecting magnetically division cores to one another using the end brackets and thereby eliminating magnetic instability.